Pressure sensors having micromechanical sensor elements are used today in machine construction, process engineering, automotive engineering, and medical technology for diverse measuring tasks. Differential pressure sensors are used to compare pressures that prevail in two chambers or media that are separated from each other. The media being measured may be liquids, gases, or even vapors.
A typical use of micromechanical differential pressure sensors in automotive engineering is comparing the exhaust gas pressure upstream and downstream from the particulate filter. Since very high and greatly variable absolute pressures occur here and the exhaust gases form an aggressive particulate-bearing measuring environment, there are increased demands on the dynamics and ruggedness of the sensor element in regard to its micromechanical structure, but also in regard to signal detection.
One possibility for differential pressure determination is detecting the two measured pressures to be compared with the aid of two independent absolute pressure sensors and then calculating the difference between the measured values thus obtained. In practice, however, this method usually does not yield satisfactory results. The reason for this is found in the insufficient measuring accuracy of the generally available absolute pressure measuring devices, which is not adequate to determine the pressure difference with sufficient accuracy, in particular in the case of wide pressure ranges and/or high absolute pressures but small differential pressures.